1. Field of the Invention
The present invention relates to the control and operation of a hybrid vehicle driveline.
2. Description of the Related Art
As a vehicle driving system, a parallel type hybrid-vehicle driving system is known in which an engine and a motor/generator are combined so that outputs of both the engine and the motor/generator can be transmitted to a driving shaft.
In order to increase the output of the motor/generator, it is effective to increase the voltage to be supplied to the motor/generator. In general, however, the supply voltage is regulated by the voltage of a battery, and therefore, the output of the motor/generator normally depends on the battery.
In view of this problem, Japanese Unexamined Patent Application Publication No. 10-191503 discloses a hybrid-vehicle driving system in which a battery is electrically disconnected from a hybrid system including a motor/generator, as required, so that the output power can follow the load.
In the above-described hybrid-vehicle driving system, however, the battery serving as a power storage means cannot be used while being disconnected. Therefore, for example, in a case in which power is generated by the motor/generator during a gear shift operation of a transmission, even when an unnecessary transient power is produced, it is not consumed by any means. For this reason, all the transient power is transmitted as the driving force, and this gives an uncomfortable feeling to the driver.